At present, there are several major types of touch screens as follows: resistive touch screens, surface-capacitive touch screens and induction capacitive touch screens, surface acoustic wave touch screens, infrared touch screens and so on. The capacitive touch screens are more widely applied, mainly in communications and consumer electronics, such as smart phones, mobile phones, multimedia players, PADs and so on.
A capacitive touch screen, which determines a touch point by sensing a change in a capacitance caused by a touch, is provided with two groups of signal lines: a driving line that emits a signal and an induction line that senses a change in a capacitance value. When a finger touches a metal layer, the finger and the surface of the touch screen form a coupling capacitor because of the existence of an electric field of the human body. The capacitor is a direct conductor for a high frequency current, whereupon the finger absorbs an extremely small current from the touch point, thereby affecting coupling of two electrodes around the touch point to change a capacitance between these two electrodes. When a mutual capacitance is detected, electrodes in the direction of the driving line emit an excitation signal in turn while all electrodes in the direction of the induction line receive the signal simultaneously, so as to acquire changes in capacitance values of intersections of all row electrodes and column electrodes, that is the capacitances of a two-dimensional plane of the touch screen. The coordinates of each touch point can be calculated according to data of a change in capacitances of a two-dimensional plane of the touch screen, thus the true coordinates of each touch point can be calculated even if there is a plurality of touch points on the screen.
With the progress of the technology of handheld mobile communication terminals having a touch screen, more and more users are using a handheld mobile communication terminal having a touch screen. A touch screen, which responses more sensitively to a conductor (e.g., a finger), brings good experience for a user. However, a mis-touch is generated easily at edges of the touch screen, when a device having the touch screen is held by hand, thus affecting user application. Especially, when a user operates, with one hand, a device having a touch screen with a large size or designed with a narrow edge, or holds the device with one hand while operates the device with the other hand, a mis-touch is generated easily on the touch screen by the hand holding the device, thus an error point may be generated on the touch screen to affect an operation of the user and user experience.
At present, there is no effective solution yet for a problem caused by a mis-touch generated when a touch screen device is held by a hand.